In a vehicle air conditioning system which is used in an Electric Vehicle (EV), a Hybrid Electric Vehicle (HEV), a Plug-in Hybrid Electric Vehicle (PHEV), or the like, a heating operation cannot be performed using combustion exhaust heat of engine cooling water or the like. In addition, exhaust heat from a travelling motor, a battery, or the like can be used instead of an engine. However, an amount of the exhaust heat is small, and thus, a heating system which has only the exhaust heat as a heat source cannot be realized. Meanwhile, a heating system using an electric heater is considered. However, since heating power consumption is increased with respect to battery capacity, there is a problem that a travel distance of a vehicle is significantly decreased due to use of the heating.
Accordingly, as the vehicle air conditioning system which is applied to the EV or the like, a heat pump type air conditioning system using an electric compressor is considered. In a case of a reverse type heat pump, pipes configuring a refrigerant circuit, a heat exchanger such as an evaporator or a condenser, or the like should be used in common under different pressure conditions of a cooling operation and a heating operation. Accordingly, a vehicle air conditioning system applied to a current engine drive type vehicle should be changed thoroughly.
Meanwhile, as described in PTL 1, an air conditioning system in which a sub condenser (interior condenser) is added to a refrigerant circuit is suggested. In this case, a heat pump type vehicle air conditioning system can be configured by adding a switching valve, a bypass circuit, and a sub condenser while using the evaporator of a current system with respect to an interior evaporator which is provided in a Heating Ventilation and Air Conditioning Unit (HVAC unit).